UNDERGROUND SPACE FOR HAZARDOUS WASTE STORAGE
UNDERGROUND SPACE FOR HAZARDOUS WASTE STORAGE
Associated Research Centers for the Urban Underground Space (ACUUS)
Solution proposed by:
ACUUS and many cities in the world
In a Nutshell:
Modern societies create large quantities of hazardous and toxic waste that pose a serious threat to urban areas. They need to be safely disposed. Underground storage of hazardous and toxic waste offers a safe and easy to monitor environment, minimizes the environmental footprint and releases valuable space at the surface.
Where and When:
The first underground repository in the world, in Herfa Neurode (Germany), opened in 1972. In Wittelsheim (France), the first one (StocaMine) opened in 1999. In Chesire (UK), the Minosus repository acquired its permit in 2006 to store hazardous waste. In Greece, the first one opened in 2010 in Lavrion area.
EU member states generate around 70 million tons of hazardous waste per year. The annual turnover of hazardous waste management services is estimated around 6 billion euros. There is an increasing demand for hazardous waste management solutions and more importantly for efficient disposal sites. In addition, the stricter environmental legislations (European Directives 1999/31 and 2003/33) enforced favor underground repositories.
The use of underground repositories for the hazardous wastes storage presents various advantages over above ground landfill sites. The natural visual screen and barrier offered by the geological medium prohibits the diffusion of the internal processes to the surface environment and consequently protects the biosphere from the disturbances and risks inherent in certain types of activities. There are clearly a better potential to control gas, or leachate production, if any, unlike above ground landfills. Since the facility is located underground, there is no effect to ground-level land uses. Additionally, the underground facility can be easily expanded to accommodate future needs.
Underground repositories are well suited for long-term or "perpetual" disposal of wastes, and especially for residues which have high leachability. They offer a unique closed environment for storage: impermeable geological layers, isolation (depth from 150 to 1000 m), very dry, stable atmosphere, allowing very long term disposal. In addition, engineering barriers can be added to natural ones, if necessary, creating further reliable sealing measures (packing, brick walls, massive damming walls) in order to fully contain the waste from any possible pathway to the biosphere. This combination ensures secure isolation of wastes which represent a hazard to human beings and the environment in above-ground landfills because of their water-solubility and concentration of toxic substances.
The main concept of underground hazardous waste disposal is to either utilize abandoned or closed mining facilities, especially salt and potash mines or to specifically develop an underground cavern in order to store the waste. These facilities are usually constructed with the “room-and-pillar” mining method. There are a lot of underground storage complexes located in deep impermeable geologic formations ensuring the waste’s isolation from the biosphere, as well as attenuation of any pollutants leaking from the contaminant source. Nevertheless, when such favorable geological conditions are not available, the development of repositories in hard rock should be taken into account. Relevant investigations and state of the art research has demonstrated the potential and competence of such repositories excavated in crystalline and sedimentary formations. In such cases the application of artificial or engineering barriers is mandatory in order to achieve the same levels of waste containment. During the operation of the facility the waste arrive at the site in appropriate drums or flexible intermediate bulk containers (commonly known as big bags), they are marked, a sample is being taken for analysis and then the waste are transferred in the underground facility. Drums and big bags are placed in the allocated safe storage areas to a maximum height determined by their contents. The location of each waste batch is recorded for future reference. Upon filling each disposal zone walls are erected so as to create physical barriers between storage zones. These walls also enable the segregation of waste and facilitate storage procedures. The main advantages of the solution are the safe disposal of the waste, the complete isolation of contaminants from the biosphere, the absence of odors and visual impact, the versatility in separating storage zones, the ability to expand the underground facility and there is no interaction between underground operations and surface land-uses
The proposed solution addresses a pressing environmental and social problem that modern urban societies are faced with. Underground waste disposal offers a safe and controlled environment where the waste are stored and monitored. The natural and artificial barriers block any possible pathways of the contaminants to the biosphere. Furthermore, an underground facility can be expanded to accommodate future needs and post-closure monitoring is limited. Hazardous waste landfills is a polluting and locally unwanted land-use, by relocating it in the underground urban authorities reclaim valuable surface areas and improve the quality of the environment.